Search engines, such as Internet search engines, have been in use for some time. Such search engines permit the user to form a search query using combinations of keywords to search through a web page database containing text indices associated with one or more distinct web pages. The search engine looks for matches between the search query and text indices in the web page database, and then returns a number of hits which correspond to URL pointers and text excerpts from the web pages that represent the closest matches.
Some Internet search engines attempt to detect when a user has entered a query incorrectly. For example, a prominent search engine employs a “Did you mean . . . ?” feature that essentially runs a spellchecker on user queries. The spellchecker attempts to detect when an entered word is misspelled by checking it against a database of common words and their misspellings. When a possible misspelling is detected, the search engine may provide to the user a prompt to invoke an alternative query in which the misspelled word is spelled correctly.
Cyc, an artificial intelligence project for building a knowledge base, provides a response feature for queries it cannot answer. A knowledge base of Cyc uses an extensive ontology that provides relationships between entities. “A town contains houses” and “a car can drive on roads” are examples of relationships coded into the ontology. When a user submits a query asking a question that Cyc can't answer, for example, “can a car drive on a handrail?” Cyc will provide to the user the closest set of inferences it has made in attempting to answer the query, such as “a car can drive on roads.” These responses thus merely show inferences made by the inference system.
Some application programs, for example, a word processor, may have a help tool that allows a user to enter a word or phrase and will display help topics containing that word or phrase, from which the user can make a selection.